Note first that the Hot Link Pro is very noise impervious. The RF shielding and input electronics are very robust.
Noise is present if Confirmation LED is glowing, even just a little, when remotes are not in use.
Try first: Check system; With Hot Link Eye already plugged in, insert power plug and observe blue LED blink once on power-up. Then unplug eye cable and only re-insert the tip of the RCA Connector. blue LED should be on full. Finish insertion and LED should turn off. Try the following…
Re-insert the RCA eye connector a few times. This breaks up any oxides on the connector.